DIY Hydronic Floor Heating

[AC_Hacker]

Mikesolar,

This low temperature floor heating information is really great in many respects. Since it is wandering a bit off topic for a Dual compressor heat pump thread, but is especially relevant information for the DIY Hydronic Floor Heating thread, perhaps you could copy your response to THIS LOCATION.

Originally Posted by Mikesolar

There is a move to SCOP over COP because we should be looking at annual bills for the real indicators.

Very interesting... I take it that SCOP is Seasonal Coefficient Of Perfromance? It does make sense that this would be a more useful measure of performance.

Originally Posted by Mikesolar

With the use of an outdoor reset mixing valve on the floor heating, we can often keep the temp to 24 -28C at milder temps which, with the right HP, could give a COP or 4 or better.

I must admit that I have never heard of an outdoor reset mixing valve before. I just googled the term and came up with THIS USEFUL PDF DOCUMENT.

It would be very helpful if youu could go into a little more detail regarding the rationale and function of this type of valve.

Originally Posted by Mikesolar

My friends in europe are putting tubing at 100mm(4") in many cases which until a few years ago I would only do in a sunroom. Now I do it most places. Tubing is a cheap one time cost.

OK, this kind of information has been very hard for me to find but I knew it was being practiced... so I really want to know more...

I certainly see the reason behind why such close spacing is being used, my questions here, regard gaining a full understanding of how it is being done, specifically:

• How to cope with bend radius problems
• What diameter tubing is being used in these installations
• What flow rate is regarded as optimal in these installations
• What are the details if construction for such floors? (poured/not poured?, built up?, the use of high-conductivity materials?, etc)

Lastly, it is very interesting that you are living in Toronto, where your average Heating Degree Days (F) = 7223 (assuming a base temperature of 68 degrees F) or Heating Degree Days (C) = 4010 (assuming a base temperature of 68 degrees C), that folks are successfully using ASHPs.

Many of our readers live in HDD-challenged areas and have a great interest in ASHPs.

Best,

-AC_Hacker

* * *

[Mikesolar]

I have bought a couple of those Taco valves but I don't like them. The orifice is so small that I could not run 5 loops of pex without the pump cavitating. The Cv is way too low. I changed them for some honeywell valves that give a much better performance. The point of the mixing valve is to reduce the temp swings in the floor that can come with using room stats. The lag is just too long.

About COP....Anyone can make a HP and claim a COP of 6, but at what conditions? Air temp of 10C and liquid temp of 25C? sure that is easy. Try air of -15C and liquid of 40C (the most you should ever need for floor heating). That is why SCOP is much better or at least state the output at various conditions so people can compare.

I have a bias towards concrete and gypcrete. I have used heat emission plates but I believe the best LONG TERM performance and longevity uses lots of thermal mass. Yes, it doesn't respond as quickly but why should it? I also don't have more than one t-stat per floor unless there is a zone with very different heat needs.

The 4" spacing still has a 6-8" loop at the end....oh well.

The HPs we build do have electric elements for backup but we also have good off peak electrical pricing which is half of the peak price so I can build up heat in the slab at night to radiate out during the day, if I wanted to.

[AC_Hacker]

Originally Posted by Mikesolar

...I have a bias towards concrete and gypcrete. I have used heat emission plates but I believe the best LONG TERM performance and longevity uses lots of thermal mass. Yes, it doesn't respond as quickly but why should it? I also don't have more than one t-stat per floor unless there is a zone with very different heat needs...

I see...

How do you get your European radiant floor information? Are there blogs that you know of where this sort of thing is being discussed? Books? Web sites?

-AC

[Mikesolar]

Originally Posted by AC_Hacker

I see...

How do you get your European radiant floor information? Are there blogs that you know of where this sort of thing is being discussed? Books? Web sites?

-AC

I still have my REHAU and WIRSBO books from 20 years ago and they have curves showing heat output at different spacing and water temps, so I have always known that i can use a lower temps at closer spacing. Simple logic. The benefit is less when using a condensing boiler so 8" became standard for gypcrete and 12" for slabs.

Now, with solar and heat pumps, spacing becomes much more important. There is a lot more time through the heating season when you can get 30C from solar vs 40C so if your system is set up for 30C.........immediate benefit.

With HPs it is all about the temp spread. The smaller the better. I will have to look at the books to see what the numbers say about 4" spacing as i haven't looked at them in a few years.

[AC_Hacker]

Thanks...

I guess I'm looking for more information regarding the bleeding edge of low-temperature heating.

I spent some time with a Watts Radiant computer program and that was quite informative. I learned, as you have, that closer spacing makes lower temperatures possible. I also learned that at the bleeding edge, higher flow rates are required, which imply more attention to optimum tube sizing, optimum tubing length, and also pump optimization. I also learned that the computer tool did not allow spaces closer than 6". It was kind of like coming to the edge of the earth...

So, the above approaches are not included in common practices in the US, as you said, 8" and 12" spacings have become the standard. But I'm not very interested in the standard, I'm much more interested in what exists beyond the standard.

If you think about how long a radiant floor might last, and then consider this chart:

...here we see that the per gallon price of #2 heating oil went from about $0.65 per gallon in Jan 02 to about $3.15 in Jan 12 (as of today, the national average is $3.97).

Would the rule of thumb from 2002, that close tube spacing were not worth the trouble when using a condensing boiler (15% greater efficiency, on average) still hold up when energy prices increase, as they have by 385%?

So, you've been in the trade a while, when do you think that energy prices will come back down, and stay down? Or do you think that they will continue to rise like they have on the chart, hitting $10 per gallon around 2040?

I'm in the camp that believes that energy prices will continue to go up, at an even faster rate, and that now is the very best time to prepare for a chilly future.

It seems to me that too many folks in the US are asleep to the situation, and that folks in Europe understand and are engaging in appropriate upgrades to their homes & businesses.

That's why I am so interested in finding out how Europeans are approaching radiant heating.

BTW, you didn't explain the rationale behind using the outdoor reset mixing valve, you just said you didn't like the Taco...

-AC

[Mikesolar]

Originally Posted by AC_Hacker

Thanks...

I guess I'm looking for more information regarding the bleeding edge of low-temperature heating.

I spent some time with a Watts Radiant computer program and that was quite informative. I learned, as you have, that closer spacing makes lower temperatures possible. I also learned that at the bleeding edge, higher flow rates are required, which imply more attention to optimum tube sizing, optimum tubing length, and also pump optimization. I also learned that the computer tool did not allow spaces closer than 6". It was kind of like coming to the edge of the earth...

So, the above approaches are not included in common practices in the US, as you said, 8" and 12" spacings have become the standard. But I'm not very interested in the standard, I'm much more interested in what exists beyond the standard.

If you think about how long a radiant floor might last, and then consider this chart:

...here we see that the per gallon price of #2 heating oil went from about $0.65 per gallon in Jan 02 to about $3.15 in Jan 12 (as of today, the national average is $3.97).

Would the rule of thumb from 2002, that close tube spacing were not worth the trouble when using a condensing boiler (15% greater efficiency, on average) still hold up when energy prices increase, as they have by 385%?

So, you've been in the trade a while, when do you think that energy prices will come back down, and stay down? Or do you think that they will continue to rise like they have on the chart, hitting $10 per gallon around 2040?

I'm in the camp that believes that energy prices will continue to go up, at an even faster rate, and that now is the very best time to prepare for a chilly future.

It seems to me that too many folks in the US are asleep to the situation, and that folks in Europe understand and are engaging in appropriate upgrades to their homes & businesses.

That's why I am so interested in finding out how Europeans are approaching radiant heating.

BTW, you didn't explain the rationale behind using the outdoor reset mixing valve, you just said you didn't like the Taco...

-AC

I don't think that the flow rate needs to go up. Remember that flow rate is based on area heat loss so for a 100,000btu heat loss and a 20 deg DT we have a 10 gpm flow rate, regardless of delivery temp. 150-130F is the same delivered heat as 100-80F. If you divide that 10gpm by 10 loops or by 20 loops, only changes the flow/per loop, not the total. It is not strictly a linear relationship due to the actual floor temps and renolds numbers for turbulence but roughly it works better with the tighter spacing. The difference is that having a higher temp is like having a higher HP car engine, it can push through a more stubborn media, such as air. Concrete is much better at taking the low temps. So if you tried to push 150f through the concrete, the heater would cycle on and off which is not good for the boiler or definately not good for a heat pump. Europeans don't use heat emission plates as almost everything there is in some form of concrete. The aluminum plates are a North American product because builders here don't want to wait for anything.

Look at the a graph of air temp vs time with an on off system. There is a lot of wasted gas or power just getting the heating source going so we will have a lot of peaks and valleys. If we are able to use a modulating boiler we can even out the curve easily and if that curve is based on a outdoor temp, we can adjust it further. Flat line indoor temp is the goal and gradual changes to water temps are desired. High HP is needed for starting but you only need 25% of that power for cruising.

I have no idea where fuel rates will go and I never anticipated fracking. Technology changes have allowed horizontal drilling so peak oil production seems to have been pushed back a few years. Cheap gas is one of the few things that will allow us to get rid of coal for power production but with oil, I know it will go up, I just don't know by how much.

[Vlad]

Originally Posted by AC_Hacker

I must admit that I have never heard of an outdoor reset mixing valve before. I just googled the term and came up with THIS USEFUL PDF DOCUMENT.

This valve is a part of my control loop. If you look at parts list I posted you can find it there.

I used taco 2 way outdoor reset valve and I love it. It works like thermostat in my system. The only difference it takes to account outdoor temperature and not indoor like thermostat. It is easily adjustable.

http://ecorenovator.org/forum/21536-post204.html

Check eBay for better pricing. I paid for my 200+

You have to follow instructions when it comes to plumbing this valve. You have to have bypass otherwise when it closes your pump will have a hard time to pump nothing

[Vlad]

Originally Posted by Mikesolar

I have bought a couple of those Taco valves but I don't like them. The orifice is so small that I could not run 5 loops of pex without the pump cavitating. The Cv is way too low. I changed them for some honeywell valves that give a much better performance. The point of the mixing valve is to reduce the temp swings in the floor that can come with using room stats. The lag is just too long.

I used this valve and pump works well. You have to have bypass. And this is not a full flow valve but mixing valve. It just adds extra hot/warm water when needed.

Originally Posted by Mikesolar

I have a bias towards concrete and gypcrete. I have used heat emission plates but I believe the best LONG TERM performance and longevity uses lots of thermal mass. Yes, it doesn't respond as quickly but why should it? I also don't have more than one t-stat per floor unless there is a zone with very different heat needs.

In my case I live in warm area. Our winter usually +5+10С day temperature and +5-5 night temperature. So because I used low mass floor system (sandwich) I can get more savings because my system can raise or lower temperature very quickly just a bit slower then air furnace. Also many people don't occupy their house during day time. Using concrete you will heat up your house for no reason when it is not occupied.

[Mikesolar]

I've been using reset mixing valves for almost 25 years. Until recently package ones were only available from Viessmann, called the Dekamatic HK1, or from Tekmar, who makes the control for Taco IIRC. (Honeywell may make a couple but they were not very popular here)

The Viessmann product is good because it comes in either a 3 way or a 4 way valve with a high Cv (high flow). We used 4 way valves before condensing boilers came along to provide low temp protection to cast iron or steel boilers when we used radiant floors.

Dekamatik-HK1-ii.pdf

Vlad, the 4 way incorporates the bypass and gives better return temp control. In the 3-way the hot goes directly into the valve and some of the return from the floor brings down the hot to floor temps. The rest goes back to the boiler. The output of the valve MUST be able to take the full flow needed by the loops without too much pressure drop and every situation is different. To me, just looking at the valve and its tiny port is a cause for concern as i believe it is fine for doing a few loops but not for a whole house.

[Vlad]

Originally Posted by Mikesolar

I've been using reset mixing valves for almost 25 years. Until recently package ones were only available from Viessmann, called the Dekamatic HK1, or from Tekmar, who makes the control for Taco IIRC. (Honeywell may make a couple but they were not very popular here)

The Viessmann product is good because it comes in either a 3 way or a 4 way valve with a high Cv (high flow). We used 4 way valves before condensing boilers came along to provide low temp protection to cast iron or steel boilers when we used radiant floors.

Attachment 2476

Vlad, the 4 way incorporates the bypass and gives better return temp control. In the 3-way the hot goes directly into the valve and some of the return from the floor brings down the hot to floor temps. The rest goes back to the boiler. The output of the valve MUST be able to take the full flow needed by the loops without too much pressure drop and every situation is different. To me, just looking at the valve and its tiny port is a cause for concern as i believe it is fine for doing a few loops but not for a whole house.

I used 2 way taco valve. It does have tiny hole when fully opened but I only add hot water trough it and rest of flow goes through bypass. Here is my set up:

http://ecorenovator.org/forum/renova...html#post21533

I have 10 zones and 10 loops and have never had a noise or vibration or anything else from pump. When outside is warm 2 way taco valve is mostly closed and water circulates through bypass which is basically return.... I did added this valve in return/bypass to create pressure difference:

https://www.pexuniverse.com/store/pr...***-valve-3196